Re: getting a TGraph from a file

Hi Roger!

On 23 Jan 2007, at 16:30, Roger Mason wrote:

> Hello,
>
> I have an elementary question: how to get a TGraph from a file.
>
> I save a TGraph object to a file. I can open the file and verify that
> the TGraph is present:
>
> root [5] TFile f("file1.txt.root","UPDATE")
> root [6] .ls
> TFile** file1.txt.root
> TFile* file1.txt.root
> KEY: TGraph Graph;1 Original data
>
> I recover the TGraph:
>
> root [7] Graph->Draw()
> <TCanvas::MakeDefCanvas>: created default TCanvas with name c1
>
> but the canvas is empty.
>

TGraph::Draw() doesn't do much without a draw option. Try Graph->Draw ("ap").

This behaviour of TGraph is quite counter-intuitive. Is there a reason why the option string does not have a default containing at least "ap"?

Ciao,

                     Roland

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